Apparatus for measuring the level of liquids



Nov. 3, 1953 O. FALK APPARATUS FOR MEASURING THE LEVEL OF LIQUIDS 3Sheets-Sheet 1 Filed Nov. 25, 1949 Nov. 3, 1953 O. FALK APPARATUS FORMEASURING THE LEVEL OF LIQUIDS Filed Nov. 25, 1949 3 Sheets-Sheet 2INK/EN roe OLAF FALK ATTORNCK Patented Nov. 3, 1953 APPARATUS FORMEASURING THE LEVEL OF LIQUIDS Olaf Falk, Oslo, Norway, assignor toAskania- Werke Aktiengesellschaft, Berlin, Friedenau, Germany, acorporation of Germany Application November 25, 1949, Serial No. 129,241

5 Claims. (Cl. 73-212) The present invention relates to an apparatus formeasuring the level of liquids.

The primary object of my invention is to provide an apparatus permittingto measure the level of a fluid with a greater accuracy than this waspossible hitherto.

Another object of my invention is to provide an apparatus permitting torecord with a great accuracy the variations of the level of a liquid.

Still another object of my invention is to combine two such apparatusfor measuring the flow output of a liquid flowing through a channelhaving a cross section of known shape and size, the one of theseapparatus measuring the level of the liquid in the channel, whilst theother apparatus measures the level of liquid indicating the hydrodynamicpressure of the moving liquid, further means responsive to these twoapparatus indicating the flow velocity.

Other objects of my invention will appear hereinafter as the descriptionof the invention proceeds, the novel features, combinations andconstruction being more particularly pointed out in the specificationand the claims hereunto appended.

The annexed drawings diagrammatically illustrate several modificationsof apparatus according to my invention.

Fig. l is a diagrammatical illustration of a first embodiment of theinvention.

Fig. 2 is a diagrammatical, partly sectional illustration of a secondembodiment.

Fig. 3 is a diagrammatical illustration of a third embodiment.

. Fig. 4 represents a diagram of a physical function.

Fig. 5 is a diagrammatical, partly sectional view of an apparatusaccording to the invention.

Fig. 6 is an elevational illustration of the apparatus shown in Fig. 5.

Fig. 7 illustrates some characteristical curves recorded with anapparatus like that represented in Fig. 5.

In Fig. l of the drawings, a reservoir 4 is shown containing anelectricity-conducting liquid 2 the level of which is to be measured forexample before and after having fed a quantity of liquid to thereservoir.

The apparatus comprises a shaft 3 journalled in fixed bearings indicatedat t. A drum 5 of insulating material and a toothed wheel ii of a wormgearing are both rigidly keyed onto the shaft 3. A metallic slip ring Iis fixed to the drum 5 and connected with a fine metallic wire 8 whichis rolled and unrolled as the drum 5 is rotated in one or otherdirection. A weight 9 is connected to the lower end of the wire 8 andtraversed by a contact rod l0 electrically connected to said wire 8. Afixed brush H slipping on the ring 1 is connected to one end of thesolenoid coil l3 of an ultra-sensitive relay, the other end beingconnected to one pole of the current source l2 the other pole beinggrounded at I4. The pivot of the spring-loaded armature lever I5 of saidrelay is connected by a conductor 16 to one phase of analternating-current network, the other phase being connected by aconductor I! to one of the terminals of a reversible electric motor S8.The other two terminals of the latter are connected by conductors l9 and26, to fixed contacts 2|, 22 alternatively cooperating with the movablecontact 23 fixed to the armature lever l5. The shaft 24 of the motor I8is connected by a revolution counter or recording device 25 with theshaft 26 to which the worm 2'! of the already cited worm gearing isrigidly fixed.

The operation is as follows:

As long as the contact rod Ill does not touch the surface of the liquid2, the energizing circuit of the relay winding l3, comprising saidcontact rod [0 and the liquid 2, is open. The springloaded armaturelever I5 then urges its movable contact 23 onto the fixed contact 22,causing the motor [8 to revolve its shaft 24, the shaft 3 and the drum 5in such a direction as to unroll the wire 8 and to lower the contact rod10 onto the surface of the liquid 2. As soon as the rod It contacts thesurface of the liquid, the energizing circuit of the relay I3 isestablished and. causes the movable relay contact 23 to be moved ontothe contact 2| and the motor I 8 and consequently the drum 5 to rotatein the opposite direction. The wire 8 is then rolled up and the contactbetween the rod Ill and the liquid 2 cut off, so that the revolvingdirection of the motor shaft 24 and of the drum 5 is reversed once more.When the surface of the liquid does not vary, these alternativemovements are continued. By proper design of the apparatus the extent ofthese movements can be made very small and consequently, the measuringaccuracy very great. When the liquid level varies, the tip of the rod 10follows these variations very closely. The amount of these variations isproportional to the number of revolutions of the shafts 24, 26,indicated by the device 25. The current passing through the contact rod10 and the liquid 2 may be amplified in some appropriate electronicamplifier before passing the relay l3. Instead of using a reversiblemotor I8, a reversing gearing and a pair of electromagnetic clutchescontrolled by said relay may be used, as shown in a further embodimentyet to be described.

If the liquid the level of which is to be measured is a non-conductor,an apparatus like that shown by Fig. 2 may be used. This apparatuscomprises a float generally indicated at 30. The float comprises aclosed ring chamber 31 and a central chamber 32 in which the liquid maytake the same level as the surrounding liquid, owing to a communicationpipe 33 protruding from the bottom wall 34 of the chamber 32. Thecentral portion 35 is shaped as a vessel for a small quantity of aconductor liquid 35 heavier than the liquid 2, of mercury for example.

The shaft 3 journalled at 4 now carries besides the wheel 6, a drum 3'!of insulating material, the middle portion of which is fitted with twoslip rings 38. Metallic wires 39 rolled on the drum 3! on both side ofthe slip rings 38 to which they are individually connected, interlacethe ends of an insulating bar 49 and have somewhat coiled lower ends 4|individually connected to two contact rods 42 traversing a weight 43made of insulating material. This weight is suspended from the bar 49 bymeans of a wire 44. Flanges 45 and 46 secured to the weight 43 and tothe upper wall 41 of float, are intended to engage each other when thefloat 30 is taken from the liquid 2. Springs 48 attached to the weightand to the float vertically yieldingly maintain these parts in such aposition with respect to each other that the points of the contact rods42, when lowered, touch the conductor liquid 36, the evaporation ofwhich is prevented by the liquid contained in the central chamber 32.

The wires 39, the contact rods 42 and the slip rings 38 cooperating withbrushes 49, are set in the energizing circuit of the relay winding I3together with the current source [2. The remaining portion of theapparatus, comprising the relay armature and contacts, the conductorsI9, 20, [6, I1, the reversible motor 18, the counting or recordingdevice 25 and the worm 21 meshing with the worm wheel 5, is similar tothe corresponding portion of the first embodiment hereabove described.

The operation of this apparatus differs from that shown by Fig. 1 onlyin that the current energizing the relay winding l3 passes through twoslip rings 38, two wires 39, two contact rods 42 and a conductor liquid36 contained in a vessel of a float.

Whilst both preceding embodiments work automatically, that of Fig. 3 ismore simple and is operated by hand. The weight 43 fitted with contactrods is attached to the lower end of a measuring tape 50 the upperportion of which is rolled on a narrow drum which is rigidly fixed to anaxle 52 journalled at 53 and provided with a crank 54 at one of itsends. Two metallic wires 55 connected to the upper ends of the contactrods 42 pass over two pulleys 56 made of insulating material and looselymounted on the axle 52., then pass over two pulleys 5'! also made ofinsulating material and pivoted on a somewhat heavy transverse bar 58(for stressing the wires) and are connected to fixed terminals 59 of acurrent-flow-indicating device comprising conductors 60, 6|, a currentsource 52 and an amperemeter or voltmeter 63, a bell or the like. Themeasuring tape 55 moves behind the window 64 of a fixed member 55, whichmay be provided with graduated index means along the window.

The operation is as follows:

The crank 54 is actuated to lower or elevate the weight 43 so that thecontact rods 42 touch the conductor liquid 36, this being indicated bythe instrument 63, and the tape 50 appearing in the opening 64 is readbefore and after each feeding of liquid 2' to or from the reservoir I.The tape 50 may indicate the level of the liquid 2 (in millimeters orinches) and/or the quantity of liquid contained in the reservoir.

It is well known to those skilled in the art that the velocity of aflowing fluid can be measured by measuring its hydrodynamic pressure,this pressure being indicated by a liquid contained in a gauging tube.The level of this liquid may easily be measured by the apparatusaccording to my invention and, therefore, this apparatus may well beused for measuring and possibly recording the fiow velocity of a fluid.

In a further embodiment, now to be described, I have provided facilitiespermitting to measure and to record the quantity of a liquid flowingthrough a channel or the like at a cross-section of known shape. Forthis purpose I use two apparatus as those set out hereabove, the one formeasuring the level of the flowing liquid, the other for measuring thehydrodynamic pressure by means of a conventional device. In knownapparatus for measuring the velocity of a liquid flowing through achannel and having a free level subject to variations, measuring-faultsare produced in the velocity measurement on the ground that saidvariations interfere in the measurement of the hydrodynamic pressure, inthat the sum of these variations and of those of the hydrodynainicpressure is read in the gauging tube intended to indicate the variationsof the hydrodynamic pressure only. Errors of this kind are eliminated bythe following arrangements.

A gauging tube of a device generally known as a Pitot tube and adaptedto measure the hydrodynamic pressure caused by the velocity V of a riverhas its mouth 'H immerged into this river. The shape of this mouth issimilar to that of the mouth of a trumpet. Tests have shown that thesuction pressure caused in the gauging tube 10 by a liquid in adirection opposite to that of the arrow V (Fig. 5) is proportional tothe square of the velocity V, as is the hydrodynamic pressure of aliquid flowing in the direction of the arrow V.

Numeral 12 designates a box having a lower wall 13, a top wall 14 andtwo intermediate walls 15 and 16. Two shafts 11 and 1B fitted with drums19 and 80, respectively, similar to drum 5 of Fig. l, are journalled inbearings 8| fixed to the wall 13, which has two slots 82, 83 parallel tothe shafts 11, 18. Metallic wires 84, 85 have their upper ends rolled onthe drums 19 and 80, respectively, connected to slip rings 86, 81 fixedon these drums, and their lower ends connected to contact rods 88, 89,respectively. Contact rod 88 is adapted to touch the upper surface ofthe flowing liquid, whilst contact rod 89 is received in the verticallyextending portion of the gauging tube 10 for contacting the surface ofthe liquid therein.

Two vertical shafts 90, 9| are journalled in the walls 13, 14 of the box12. Worms 92, 93 rigidly fixed to shafts 90, 9|, respectively, mesh withworm wheels 94, 95 rigidly fixed to the shafts I1, 18, respectively.Recorder actuating drums 96, 9'! rigidly fixed to those portions of theshafts 90, 9| which extendbetween the intermediate walls 15, 16 are bothprovided with intercrossing right-handed and left-handed helicoidalgrooves 98 (see also Fig. 6). The portions of the shafts 90, 9| whichextend between the walls 14,

16 each carry a toothed wheel 99, I00, respectively, rigidly fixedthereto, a pair of electromagnetic clutches IOI, I02 and I03, I04,respectively, also rigidly fixed thereto, and pairs of bevel gears I05,I06, respectively, loosely mounted thereon and adapted to cooperate withthe electromagnetic clutches. The bevel gears I05 permanently mesh witha bevel gear I01 and bevel gears I06 permanently mesh with a bevel gearI08. The gears I01, I08 are rigidly fixed to an horizontal shaft I09journalled in brackets IIO fixed to the wall 14, and connected by a wormgearing III to the driving shaft II 2 of an electric motor II3.

A third recorder actuating drum H4 and a coaxial sleeve II5 arejournalled in the walls 15, 16. Drum I I4 is rigidly connected with atoothed wheel II6 meshing with a gear I I1 meshing with gear 99 andbeing pivoted at I I8 on the wall 16. In a similar way sleeve H5 isrigidly connected with a toothed wheel I I9 meshing with a toothed wheelI meshing with toothed wheel. I00 and being pivoted at I2I on the wall16. The sleeve II5 has a longitudinal slot I22 which is traversed by apin I23 engaging a groove I24 (later to be described in detail) providedon the periphery of drum II 4 and being fixed to guide ring I25 slidablymounted on sleeve II5.

Three slides I25, I21, I28 are mounted on guide rods I29, I30, I3I,respectively, of polygonal cross section. These slides are fitted withstylus I32, I33 and I34, respectively, extending towards a tape ofrecording paper I 35 the ends of which are rolled on two drums I36, I31journalled in bearings fixed to the walls 15, 16, drum I31 being adaptedto be driven by a clock movement or another synchronous motor (notrepresented). Pins I38 are revolvably mounted onto the slides I26, I 28and engage the grooves 98 provided on the drums 96, 91. At the ends ofthe drums 96, 91 these grooves are filled with copper solderedin, asshown at I39 (Fig. 6), so that the pin I38 when arriving at one end ofthe left-handed groove, passes into the right-handed groove uponrotation of the drums. The tip of each pin I38 has a cross-section inthe shape of a segment of a circle (as shown in Fig. 6) to enable thepin to be automatically revolved over a small angle at such a returnpoint.

The electromagnetic clutches I0 I I 04 are each provided with two sliprings. The first slip rings of the clutches IOI, I02 are connected inparallel with one pole of a current source I40 the other pole of whichis connected to the spring-loaded armature lever I4I of a relay coilhaving windings I42. The second slip rings of the clutches MI, I02 areindividually connected with two fixed contacts I43, I44 of this relay.One of the ends of the relay winding I42 is connected to a brush I45engaging the slip ring 86 connected to the contact rod 88, whilst theother end of the winding is connected to one pole of a current source I46 the other end of which is set to ground at I41. A similar arrangementis provided for the control of the electromagnetic clutches I03, I04.

The operation is as follows:

With motor I I3 rotating in one constant direction as long as theapparatus is in use and with the clock movement feeding the paper tapeI35. the slides I26, I28 are brought into an arbitrary initial positionby holding the contact rods 88 and 89 on the surface of water containedin a vessel set to ground, said surface being at a predetermined level.whilst slide I21 is brought into its zero-position manually. A stylusI48 guided in a slot of casing 12 is then brought to the same level asstylus I 38, and a similar stylus I49, at the same level as stylus I33.The stylus I32, I33, I34 draw horizontal lines a, b, 0, respectively,which end at the points (11, b1, 01 at the moment when the vessel istaken away (Fig. 7). The horizontal lines recorded by the stylus I48,I49 are in register with said lines ending at m, bl, 01. The contactrods 88, 89 are then lowered onto the surfaces of the river and of theliquid contained in tube 10, respectively, because, the energizingcircuits of the relay windings I42 being open, the clutches IOI, I03transmit the rotation of shaft I59 to the shafts 90, 9I, to rotate thedrums 19, in a direction causing unrolling of the wires 84, 85. Therotations of the shafts 90, 9I are also transmitted to the drum H4 andto sleeve II5, these two parts rotating in the same direction at thesame speed. Ring I25 is therefore not shifted on sleeve H5 and slide I21and stylus I33 are not moved, whilst the stylus I32 and I34 are moved bydrums 96, 91, respectively. The line portions recorded on the tape I35are those extending between the points a-'1a2, b1b2 and 01C2,repectively. The velocity V is supposed to be zero; the points (12 and02, therefore, are located on the same horizontal line.

Assuming that the level of the river remains unchanged for a certainperiod during which the flow velocity of the water increases from azerovalue V2 to a value V3, the contact rod 88 will not change itsposition, nor will the slide I26 and the stylus I32 controlled thereby.However, the level of the liquid in the gauging-tube 10 rises, causingthe mechanism controlling the position of the contact rod 89 and of theslide I28 and stylus I34 to change the positions of these parts. It iswell known that the height H by which the level of the liquid containedin the tube 10 is raised above that of the surface of the river is givenby the equation.

where k1 is a constant value to be determined by tests, and V thevelocity.

If the direction of flow is opposite to that represented in the drawing,the corresponding equation will be:

where k2 is another constant value to be determined by tests. 7

In the latter case, the level of the liquid contained in the tube 19will be below that of the surrounding surface. a

The diagram representing the relation between the values of V and thoseof H will therefore comprise two branches of parabolas, as shown in Fig.4. When a sheet of paper bearing these curves, is wound on the cylinderI M, with the direction V parallel. to the axis of the cylinder, saidcurves will exactly register with the groove I24 provided on thiscylinder, or rather, this groove is made accordingly: It is a helicoidalgroove having a parabolic pitch. It will now be easy to understand thatif the velocity V of the moving liquid grows constantly, thecorresponding line portion b2-b3 recorded on the paper tape I35 will bea straight inclined line whilst the line 02-423, representing the heightH, is represented by a branch of a parabola.

If thereafter the level of the river as well as its flow velocity remainconstant, portions of curves (Iii-a4, b3b4 and Cs04 will be recorded,all these portions being horizontal straight lines.

If subsequently the level of the river rises constantly, whilst its flowvelocity remains unchanged, curve portions as those indicated at (Ii-as,b4-b5 and c4-c5 are recorded.

Assuming that the water level remains unchanged during a subsequentperiod, during which. the flow velocity drops constantly to a zero valueand thereafter to a negative value, according to line b5b5S-b6, linea5--as will be a horizontal straight line, whilst line c5-ce will becomposed of three parabolic portions. Point 054 corresponds to velocityzero, the return point at the lower edge of the tape being caused by pinI38 passing from the right-handed groove on drum 9'! to the left-handedgroove thereon (or inversely). To calculate the hydrodynamic pressuredifference between points Cs and co, one has merely to add the heightsof these points above the horizontal line passing through the returnpoint.

If thereafter the level of the river is lowered constantly, whilst theflow velocity remains unchanged, the curve as--a'z may be formed asshown, with a return point ae-7 caused by pin I38 reaching the lower endof the drum 96. The difference of levels may again be obtained by addingthe diagram heights as, aw. The velocity curve is represented by ahorizontal line bc-b7, whilst line ce-c'z is an inclined straight line.

It is easily to be understood that variations of the level of say 1millimeter may produce a movement of the slides I26 and I28 over 10millimeters, for example, so that the measuring accuracy is very great.A similar accuracy may be obtained in the velocity-measurement.

Whilst in the above discussions simple changes independently of eachother in any manner without changing the method of operation of theapparatus. It is an object of the present inven-- tion to provide meansfor recording the curves indicating the variations of the water level,of

those of the water velocity and of those of the -,.J

level summarized with those of the hydrodynamic pressure, on a singletape, the curves instantaneously illustrating the changes of flowconditions of the river.

Although the foregoing description is necessarily of a detailedcharacter, in order that the invention may be completely set forth, itis to be understood that the specific terminology is not intended to berestrictive or confining and that various rearrangements of parts andmodifications of details may be resorted to without departing from thescope or spirit of the invention as herein claimed.

What I claim is:

1. An apparatus for measuring levels of nonconductor liquids, comprisingin combination, a stationary revolvable shaft, an insulating drumrigidly connected to said shaft, two metallic wires having each an endportion wound on said drum, two contact rods individually suspended onand connected to the other ends of said wires, a float having a chambercommunicating with the liquid and having a bottom wall comprising adepressed portion, an electrically conductive liquid in said depressedportion and adapted to be engaged by said contact rods, two slip ringsfixed on said drum and individually connected with said wire portions,two fixed brushes individually engaging said slip rings, a relay havinga coil, electric conduit means comprising said conductive liquid,

said contact rods, said wires, said slip rings, said brushes, said relaycoil, and a current source, reversible rotary driving means for saidshaft connected with said relay for controlling the direction ofrotation of said shaft for lowering said contact rods when said circuitmeans are not current-carrying and for raising said contact rods whensaid circuit means are currentcarrying, and means indicating the extentof rotation of said shaft.

2. An apparatus for measuring the level, the velocity, and the volume ofan electrically conductive liquid flowing through a channel, comprisingin combination, a Pitot tube; two liquid level measuring apparatus, onefor measuring the level of the flowing liquid, the other for measuringthe level of the liquid in said Pitot tube, each of these two apparatuscomprising a stationary revolvable shaft, an insulating drum rigidlyconnected to said stationary shaft, a me tallic wire having an endportion wound on said drum, a contact rod suspended on the other end ofsaid wire, a slip ring on said drum, connected to said wire portion, afixed brush engaging said slip ring, a relay having a coil, electriccircuit means comprising means permanently in contact with said liquid,said contact rod, said wire, said slip ring, said brush, said relaycoil, and a current source, reversible rotary driving means for saidstationary shaft connected with said relay for controlling the directionof rotation of said shaft for lowering said contact rod when saidcircuit means are not current-carrying and for raising said contact rodwhen said circuit means are current-carrying, an actuating drumoperatively connected with said insulating drum to be rotated therewith,a stylus-carrying slide guided for movement in a direction parallel tothe rotation axis of said actuating drum; a third actuating drumoperatively connected with the actuating drum of the apparatus measuringthe level of the liquid to be rotated with said last mentioned drum, ahelicoidal groove having a parabolic pitch on said third drum; a sleevecoaxial with and surrounding said third drum and operatively connectedwith the actuating drum of the apparatus measuring the level of theliquid in said Pitot tube so as to be rotated with said actuating drum,said sleeve having a longitudinal slot; a ring surrounding said sleeveand being coaxial slidable thereon and having a circumferential groove;a pin being fixed to said ring, traversing said longitudinal slot andengaging the groove on the third actuating drum, a third stylus-carryingslide guided to move parallel to the rotation axis of said third drumand engaging said circumferential groove, a recordertape arranged forengagement by the stylus of said three stylus-carrying slides, and meansfor advancing said recorder-tape in a direction substantiallyperpendicular to the paths of said stylus-carrying slides.

3. An apparatus according to claim 2, said driving means comprising anelectric-motor havtlividually rigidly connected with said drum shaftsadjacent to said loosely mounted bevel gears and controlled by saidrelays for individually clutching a bevel gear to its shaft.

4. An apparatus according to claim 2, said first two actuating drumshaving at their periphery intercrossing left-handed and righthandedhelicoidal grooves closed adjacent to the intercrossings at the ends ofthe recorder-drums, and pins individually and revolvably mounted on thecorresponding stylus-carrying slides and having each a tip ofsegment-shaped cross section engaging said helicoidal grooves.

5. An apparatus for measuring the level of a. liquid, comprising, incombination, a rotatable shaft, two electrically conductive flexiblemembers adapted to be wound on and unwound from said shaft, each memberhaving one end connected with said shaft and having a free end, a. floatfloating on the liquid whose level is to be measured, an electricallyconductive liquid in said float, a contact means suspended at the freeends of said flexible members and vertically yieldingly connected withsaid float, said contact means comprising two contact rods individuallyelectrically connected with said flexible members and electricallyinsulated from one another and having points positioned adjacent to thesurface of the electrically conductive liquid in said float, an electriccircuit comprising a solenoid, a source of electricity connected throughsaid solenoid in series with said two flexible means, said circuit beingclosed and said solenoid being energized upon contact of said pointswith the liquid in said float, power means connected with said shaft forrotating same and comprising means adapted to be actuated by saidsolenoid for controlling the direction of rotation of said shaft, thelatter being rotated to unwind said flexible members from said shaftupon removal of said points from the liquid in said float, and beingrotated to Wind said flexible members on said shaft upon contact of saidpoints with the liquid in said float, and means connected with saidshaft for indicating the number of revolutions of said shaft made ineither direction of rotation.

OLAF FALK.

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